Patch "NET: Fix /proc/net/arp for AX.25" has been added to the 4.4-stable tree

Patch "NET: Fix /proc/net/arp for AX.25" has been added to the 4.4-stable tree

[gregkh]

This is a note to let you know that I've just added the patch titled

    NET: Fix /proc/net/arp for AX.25

to the 4.4-stable tree which can be found at:
    http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary

The filename of the patch is:
     net-fix-proc-net-arp-for-ax.25.patch
and it can be found in the queue-4.4 subdirectory.

If you, or anyone else, feels it should not be added to the stable tree,
please let <stable@vger.kernel.org> know about it.


>From foo@baz Thu Jun 15 11:13:01 CEST 2017
From: Ralf Baechle <ralf@linux-mips.org>
Date: Tue, 23 May 2017 21:53:37 -0400
Subject: NET: Fix /proc/net/arp for AX.25

From: Ralf Baechle <ralf@linux-mips.org>


[ Upstream commit 4872e57c812dd312bf8193b5933fa60585cda42f ]

When sending ARP requests over AX.25 links the hwaddress in the neighbour
cache are not getting initialized.  For such an incomplete arp entry
ax2asc2 will generate an empty string resulting in /proc/net/arp output
like the following:

$ cat /proc/net/arp
IP address       HW type     Flags       HW address            Mask     Device
192.168.122.1    0x1         0x2         52:54:00:00:5d:5f     *        ens3
172.20.1.99      0x3         0x0              *        bpq0

The missing field will confuse the procfs parsing of arp(8) resulting in
incorrect output for the device such as the following:

$ arp
Address                  HWtype  HWaddress           Flags Mask            Iface
gateway                  ether   52:54:00:00:5d:5f   C                     ens3
172.20.1.99                      (incomplete)                              ens3

This changes the content of /proc/net/arp to:

$ cat /proc/net/arp
IP address       HW type     Flags       HW address            Mask     Device
172.20.1.99      0x3         0x0         *                     *        bpq0
192.168.122.1    0x1         0x2         52:54:00:00:5d:5f     *        ens3

To do so it change ax2asc to put the string "*" in buf for a NULL address
argument.  Finally the HW address field is left aligned in a 17 character
field (the length of an ethernet HW address in the usual hex notation) for
readability.

Signed-off-by: Ralf Baechle <ralf@linux-mips.org>
Signed-off-by: David S. Miller <davem@davemloft.net>
Signed-off-by: Sasha Levin <alexander.levin@verizon.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
---
 net/ipv4/arp.c |   12 ++++++------
 1 file changed, 6 insertions(+), 6 deletions(-)

--- a/net/ipv4/arp.c
+++ b/net/ipv4/arp.c
@@ -1250,7 +1250,7 @@ void __init arp_init(void)
 /*
  *	ax25 -> ASCII conversion
  */
-static char *ax2asc2(ax25_address *a, char *buf)
+static void ax2asc2(ax25_address *a, char *buf)
 {
 	char c, *s;
 	int n;
@@ -1272,10 +1272,10 @@ static char *ax2asc2(ax25_address *a, ch
 	*s++ = n + '0';
 	*s++ = '\0';
 
-	if (*buf == '\0' || *buf == '-')
-		return "*";
-
-	return buf;
+	if (*buf == '\0' || *buf == '-') {
+		buf[0] = '*';
+		buf[1] = '\0';
+	}
 }
 #endif /* CONFIG_AX25 */
 
@@ -1309,7 +1309,7 @@ static void arp_format_neigh_entry(struc
 	}
 #endif
 	sprintf(tbuf, "%pI4", n->primary_key);
-	seq_printf(seq, "%-16s 0x%-10x0x%-10x%s     *        %s\n",
+	seq_printf(seq, "%-16s 0x%-10x0x%-10x%-17s     *        %s\n",
 		   tbuf, hatype, arp_state_to_flags(n), hbuffer, dev->name);
 	read_unlock(&n->lock);
 }


Patches currently in stable-queue which might be from ralf@linux-mips.org are

queue-4.4/net-fix-proc-net-arp-for-ax.25.patch
queue-4.4/net-mkiss-fix-panic.patch